The present invention relates to dental amalgam alloy mixtures and more particularly to low silver dental alloy mixtures of silver, tin, copper, and zinc which are improved by adding of Cu.sub.6 Sn.sub.5, Cu.sub.3 Sn or a mixture thereof.
Prior to the present invention, dental amalgam alloys generally contained from about 68 to about 72% by weight of silver, the remainder being composed of tin, copper, and zinc, although the inclusion of gold, indium, manganese, etc. is not uncommon. The high cost of silver warranted exploration of reduced silver content of dental amalgam alloys and the use of less expensive manufacturing techniques. Many patents have been granted on dental amalgam alloys trying to reduce the silver content. Copper was the element mostly used to reduce the silver content in the alloys. These new alloy systems focused on the addition of greater amounts of copper, in effect, to reduce and/or eliminate the weak, corrosive Gamma II phase (Sn.sub.7 Hg); in the amalgam, other elements and metallurgical techniques were incorporated such as, the blending of brazing alloys with conventional or non-conventional dental alloys, the adding of indium, manganese, gold, etc., and the producing of low silver (40%) and high silver (60%) single phase non-conventional spherical alloy compositions. Many of these systems include the lathe-cut and/or spherical or irregular shaped alloy particles with varying ranges of particle size distribution. Spherical and/or irregular shaped particles are produced by water and/or gas atomization, a technology that is well known in the art.
U.S. Pat. No. 4,015,981 (Rogova et al) disclosed an alloy consisting of gallium, tin and copper in the absence of silver. This alloy was prepared by mixing together a eutectic liquid gallium-tin alloy with a powdered copper, tin alloy of the formula Cu.sub.3 Sn. U.S. Pat. No. 4,234,339 (Aliotta et al) teaches a corrosion resistant dental alloy mixture of three alloys each containing silver, tin, and copper and being in the form of spherical particles, randomly shaped particles, and flake-like particles. U.S. Pat. No. 4,039,329 (Youdelis) teaches a mixture of 75% silver and about 25% tin as a base alloy in combination with indium up to 30%. This patent teaches that a portion of the base alloy can optionally be substituted with up to 6% copper and up to 2% zinc. None of the above patents teach the present invention.